C#上传图片添加水印

using (var memoryStream = new MemoryStream())
{
    file.CopyTo(memoryStream);
    using (var img = Image.FromStream(memoryStream))
    {
        if (GlobalData.SiteData.EnableImageMask)
        {
            using (Graphics g = Graphics.FromImage(img))
            {
                Font drawFont = new Font("宋体", 24f);
                SolidBrush drawBrush = new SolidBrush(Color.FromArgb(75, Color.Black));

                StringFormat sf = new StringFormat();
                sf.Alignment = StringAlignment.Center;
                sf.LineAlignment = StringAlignment.Center;
                var mtxSave = g.Transform;
                var mtxRotate = g.Transform;
                mtxRotate.RotateAt(-45, new PointF(img.Width / 2, img.Height / 2));
                g.Transform = mtxRotate;
                //g.DrawString("YES dotnet开发平台", drawFont, drawBrush, new RectangleF(0, 0, img.Width, img.Height-20), sf);
                //g.DrawString("www.yesdotnet.com", drawFont, drawBrush, new RectangleF(0, 20, img.Width, img.Height), sf);

                //g.DrawString("YES dotnet开发平台" + System.Environment.NewLine + "www.yesdotnet.com", drawFont, drawBrush, new RectangleF(0, 0, img.Width, img.Height), sf);
                g.DrawString(GlobalData.SiteData.ImageMaskValue, drawFont, drawBrush, new RectangleF(0, 0, img.Width, img.Height), sf);
                g.Transform = mtxSave;
            }
        }
        img.Save(filename);
    }
}